Ni-Ti Shape Memory Alloy Bone Anchor for Controlled Motion
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Solution Overview
Problem
Existing dynamic bone anchors lack the ability to allow controlled limited motion after anchoring, and conventional manufacturing methods do not utilize the full potential of nickel-titanium based shape memory alloys for enhanced elasticity and overload protection.
Innovation Solution
A dynamic bone anchor featuring a nickel-titanium based shape memory alloy core member with superelastic properties, allowing for rotational and translational movements, and a manufacturing method that leverages the shape memory effect to create a strong press-fit connection between the core and anchor members, enabling modular design and improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dynamic bone anchor uses conventional materials without superelastic properties, then the manufacturing process is simpler, but the degree of possible movement and elasticity is reduced
Solution Approach 1:
The patent applies parameter changes by utilizing the phase transition properties of nickel-titanium shape memory alloy. The material transitions between martensite and austenite phases, enabling superelastic behavior that allows the core member to undergo significant deformation and recovery, thereby increasing the degree of possible movement while maintaining manufacturability through controlled thermal processing.
Solution Approach 2:
The patent employs composite materials by using nickel-titanium shape memory alloy for the core member, which combines the properties of shape memory effect and superelasticity. This material selection enables both high adaptability for movement and controlled manufacturing through established metallurgical processes, resolving the contradiction between movement capability and manufacturing ease.
2Ease of operation
If a dynamic bone anchor uses rigid materials, then the structural strength is higher, but the ability to perform limited motion and provide overload protection is reduced
Solution Approach 1:
The patent applies dynamics by designing the core member with superelastic properties that allow it to dynamically adjust its stiffness based on applied load. Under normal physiological loads, the material exhibits flexible behavior enabling controlled limited motion, while under excessive loads, the superelastic mechanism provides overload protection through stress-induced martensite transformation, maintaining structural integrity.
Solution Approach 2:
The patent utilizes phase transitions of nickel-titanium alloy between austenite and martensite phases to achieve both motion capability and strength. The phase transition mechanism allows the material to absorb and dissipate energy during deformation, providing both the desired limited motion and structural strength without requiring separate components.
3Adaptability or versatility
If the bone anchor is designed as a monolithic structure, then the manufacturing process is simpler, but the ability to provide modular design for customizable dynamic characteristics is reduced
Solution Approach 1:
The patent applies segmentation by dividing the bone anchor into distinct functional components: the anchor member for bone engagement and the core member with superelastic properties for motion control. This modular segmentation allows independent optimization of each component and enables customization of dynamic characteristics by selecting different core member geometries or material properties without redesigning the entire structure.
Solution Approach 2:
The patent implements universality by designing the core member to serve multiple functions: providing structural support, enabling controlled motion, offering overload protection, and facilitating modular assembly. The superelastic nickel-titanium material inherently provides both mechanical strength and elastic recovery, eliminating the need for separate components and reducing overall structural complexity despite the modular design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dynamic bone anchor achieves increased mobility and overload protection due to superelastic properties, allowing for controlled limited motion and a stronger press-fit connection, while being designed as a modular system for customizable dynamic characteristics.
Implementation Method 1
The core member is made, at least partially, of a material comprising a nickel-titanium (Ni—Ti) based shape memory alloy having superelastic properties
Implementation Method 2
Superelasticity, sometimes called pseudoelasticity, involves the creation of stress-induced martensite which simultaneously undergoes strain when it is formed to release the applied stress. When the applied stress is released, the thermally unstable martensite reverts to austenite, and the strain returns to zero
Implementation Method 3
The method of manufacturing such a dynamic bone anchor makes use of the shape memory effect of the material of the core member
Data Source
AI summary
A dynamic bone anchor includes an anchor member having first and second ends and a tubular section between the ends, a longitudinal axis extending from the first to second end, an outer surface, and a bone engagement structure for engaging a bone on at least a portion of the outer surface; and a longitudinal core member having a first portion and a second portion configured to be received in the tubular section and to connected to the anchor member, with the first portion configured to be spaced apart from the anchor member and movable with respect to it. The core member is made at least partially of a nickel-titanium (Ni—Ti) based shape memory alloy such that its shape after transitioning from a martensitic to austenitic phase is configured to result in a press-fit connection between the second portion and the anchor member with the second portion in the austenitic phase.